ARID1A Loss in Neuroblastoma Promotes the Adrenergic-to-Mesenchymal Transition by Regulating Enhancer-Mediated Gene Expression [ChIP-seq]

Gene mutations in components of SWI/SNF chromatin-remodeling complexes are found in approximately 20% of all human cancers, with ARID1A being the most frequently mutated subunit. In neuroblastoma, sequence alterations of ARID1A were identified in 6% of primary tumors and cell lines, and this gene is hemizygously deleted in at least 87% of cases with chromosome 1p deletion, which almost always accompanies MYCN gene amplification and is the most common deletions in high-risk subtypes of this tumor. However, the role of ARID1A haploinsufficiency in neuroblastoma pathogenesis and the mechanisms involved remain unclear. Here, we show that disruption of ARID1A homologs in a zebrafish model accelerates the onset and increases the penetrance of MYCN-driven neuroblastoma by increasing cell proliferation in the sympathoadrenal lineage. Depletion of ARID1A in human NGP neuroblastoma cells promoted the adrenergic-to-mesenchymal transition with changes in enhancer-mediated gene expression due to alterations in the genomic occupancies of two distinct SWI/SNF assemblies, BAF and PBAF. Our findings indicate that ARID1A is a haploinsufficient tumor suppressor in MYCN-driven neuroblastoma, whose depletion enhances tumor development and promotes the emergence of the more drug resistant mesenchymal cell state. Overall design: ChIP-Seq for SS18, ARID2, BRG1, H3K4Me3 and H3K27Ac in control and two ARID1A mutant NGP cells